The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Network communication systems commonly used at present include optical network communication system and radio communication system. The description of the two types of systems is provided as follows.
The optical network communication system includes optical access networks (generally called FTTx). FIG. 1 shows the network architecture of the FTTx, FIG. 2 shows reference architecture of an Optical Access Network (OAN) based on the network architecture in FIG. 1. An OAN as shown in FIG. 2 includes a Customer Premise Network (CPN), an Access Network (AN) and a Service Node Function (SNF).
The AN in the OAN includes an optional Adaptor Function (AF) adapted for conversion between an Optical Network Unit (ONU)/Optical Network Terminal (ONT) interface and a User Network Interface (UNI). When the AF is integrated into the ONU, the reference point (a) can be cancelled. The AF may also be installed behind an Optical Line Terminal (OLT) and adapted for conversion between the OLT interface and a Service Network Interface (SNI). In the optical network, the AF can be regarded either the function of the CPN or the function of the AN.
The major network elements of the CPN and AN in the OAN include: OLT, Optical Distribution Network (ODN), ONU or ONT and AF. The T is the reference point of the UNI and the V is the reference point of the SNI. The OLT provides network interface for the ODN and is connected to one or multiple ODNs. The ODN provides data transport for the OLT and the ONU. The ONU provides user side interface for the OAN and is connected to the ODN. A CPE is connected to the AF via the UNI (e.g., a Digital Subscriber Line DSL). The AF converts a packet from the UNI format into a format compatible with the (a) interface (e.g., Ethernet link) connected to the ONU. The ONU further converts the packet into a format compatible with ODN transmission (e.g., Ethernet Passive Optical Networks (EPON) packet, Gigabit Passive Optical Network (GPON) generic framing). Finally the OLT converts the packet into an SNI (e.g., Ethernet link) packet format and accesses the service node.
The radio communication system may include 3G or 2G radio communication system. The reference architecture of the 3G and 2G radio communication systems is shown in FIG. 3, mainly including a Radio Access Network (RAN) and a Core Network (CN), in which the RAN is adapted to provide all radio functions and the CN is adapted to process voice calls and data connections within the radio communication system and for interaction with and routing to external networks. In the radio communication network, the CN is divided logically into a Circuit Switched (CS) Domain and a Packet Switched (PS) Domain.
As shown in FIG. 3, the radio communication network includes the following function entities:
Base Station (BS): the BS is called Base Transceiver Station (BTS) in the Global System for Mobile communications (GSM), the General Packet Radio Service (GPRS), the Code Division Multiple Access (CDMA) and CDMA2000 systems, and is called Node B in the Wideband Code Division Multiple Access (WCDMA) and Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) systems;
Base Station Controller (BSC): the BSC is called Radio Network Controller (RNC) in the WCDMA; and
Packet Control Function (PCF) in the CDMA2000: the PCF is between the BSC and the Packet Data Serving Node (PDSN) and adapted to provide packet data service support; the PCF as a part in the radio access network can be integrated with the BSC or be a standalone device.
The component of the conventional radio communication system is described in detail with reference to a WCDMA system.
The UMTS Terrestrial Radio Access Network (UTRAN) of the WCDMA system employs the lu series interfaces including lu, lur and lub interfaces. Each of the interfaces consists of a Radio Network Layer (RNL) and a Transport Network Layer (TNL) according to the UTRAN interface general protocol model division protocol stack, in which:
the lu interface is an open standard interface via which the UTRAN and the CN are connected, the control plane protocol of the lu interface includes the Radio Access Network Application Part (RANAP) and the user plane protocol of the lu interface is the General data Transport Protocol (GTP);
the lur interface is a distinctive UMTS interface between RNCs and adapted for mobile management of the mobile stations in the RAN, e.g., when a mobile station switches from one RNC to another in a soft switching, the data of the mobile station is all transferred via the lur interface from the working RNC to the candidate RNC; the lur interface is also an open standard interface, the control plane protocol of the lu interface is the Radio Network Subsystem Application Protocol (RNSAP) and the user plane protocol of the lu interface is the lur Frame Protocol (lur FP);
the lub interface is an open standard interface between the Node B and the RNC, the control plane protocol of the lub interface includes the NBAP and the user plane protocol of the lub interface is the lub FP.
The Node B in the WCDMA system includes a radio transceiver and a baseband processing part. The Node B is connected to the RNC via a standard lub interface and mainly adapted for physical layer protocol processing of the Uu interface. The major functions of the base station include spread spectrum, modulation, channel coding, despread spectrum, demodulation, channel decoding and the conversion between a baseband signal and a radio frequency signal.
The RNC in the WCDMA system is adapted to control radio resources of the UTRAN, including broadcast distribution and system admission control, mobility management such as switching and RNC relocation management, and radio resource management and control such as macro diversity combination, power control, and radio bearer allocation.
The radio interface protocol stack between the UE and UTRAN includes multiple protocols implemented in different nodes in the radio access network. The protocols are shown in FIG. 4, including:
Radio Resource Control (RRC) protocol, implemented in the UE and RNC and adapted for managing RRC connections and radio bearers, paging/broadcasting, mobility management, and configuring the parameters of other protocol entities in the radio interface protocol stack;
Radio Link Control (RLC) protocol, implemented in the UE and RNC and adapted for user data transport, and the RLC provides three data transport modes for transport service data with different QoS requirements;
Medium Access Control (MAC) protocol, usually implemented in the UE and RNC and adapted to select appropriate transport format for user data and map logic channel onto transport channel; also implemented in the Node B for some special channel types;
Packet Data Convergence Protocol (PDCP), implemented in the UE and RNC, adapted for compressing and decompressing headers of IP data traffics in transmitting and receiving entities respectively, e.g., for combinations of Transmission Control Protocol (TCP)/Internet Protocol (IP) or Real-Time Transport Protocol (RTP)/User Datagram Protocol (UDP)/IP header compression pattern and corresponding network layer transport layer or upper layer protocols; forwarding PDCP Service Data Units (SDU) from non-access stratum to the RLC layer while transmitting user data; and when lossless Serving Radio Network Subsystem (SRNS) relocation is supported, forwarding the PDCP-SDUs and corresponding serial numbers to multiplex multiple different radio bearers onto one RLC entity.
The Broadcast/Multicast Control (BMC) functions in the WCDMA system include: storing cell broadcast messages; monitoring service traffics and requesting radio resources for Cell Broadcast Service (CBS); dispatching BMC messages; sending BMC messages to a UE; and sending cell broadcast messages to a upper layer (e.g., Non Access Stratum (NAS)).
Because the Node B in the conventional protocol stack processes physical layer protocols only, the self-adaptive technique that makes judgment based on resource management needs to be implemented in the RNC, therefore the traffic from the radio communication network to a terminal has to travel in two phases: from the RNC to the Node B and from the Node B to the terminal, and the traffic from the terminal to the radio communication network travel also in two phases in a reversed order.
Such process inevitably leads to the following problems:
As the traffic needs to pass the lub interface, a lag time of the process is longer, and therefore the processing capacity of the Node B and the statistical division multiplexing rate of resource transmission at the lub interface are decreased.
The retransmission mechanism of the RLC layer between the RNC and the UE lowers the throughput rate of the radio communication network when the lub interface shows large lag time.
The outer power control algorithm in the radio communication network is unable to adjust the target signal interface ratio (SIRtarget) according to the changes in the air interface when the lub interface shows large lag time.
The cell load information in the radio communication network is reported by the Node B regularly, however, when the process described above occupies a large amount of the lub interface resources, the cell load information cannot be reported in time and the RNC therefore will be unable to acquire accurate realtime cell load information.
Along with the rapid development of network communication technology, the network communication industry has begun to seek best data transmission performance on the basis of the merits of varieties of networks, however, the interconnection between the 3G or 2G radio communication network and the OAN has not been achieved in the conventional technology.
Furthermore, it can be seen easily from the description above that the protocol structure of the conventional radio communication network, in which all upper access stratums are arranged in the RNC, is unable to guarantee data transmission of high speed and high efficiency when self-adaptive adjustment and feedback control techniques are applied, hence the conventional protocol structure does not meet the demand for high-speed data transmission.